The main objective of this research project is to understand how in utero Bisphenol A (BPA) exposure affects fetal gonadal development and reproduction in adulthood in mice. In utero exposure to estrogenic endocrine disruptors such as diethylstilbestrol (DES) is known to cause sex organ malformation, reproductive carcinogenesis, and fertility defects in both male and female in humans and rodents. Based on DES studies, it is proposed that in utero exposure to other endocrine disruptors, particularly those that work through estrogen receptors, may lead to reproductive diseases in adulthood. BPA, a chemical used in synthesis of plastics, exhibits estrogenic activities and deleterious effects on reproduction when given to adult rodents. BPA is detected in serum of pregnant women, umbilical cord blood, and fetal plasma, indicating that developing fetuses are exposed to BPA. Although effects of BPA on adult reproductive organs have been studied extensively, impacts of in utero BPA exposure particularly on fetal gonadal development are not well understood. In vitro experiments have suggested that BPA, similar to other estrogenic compounds, could bind to classical nuclear estrogen receptors (ERa or p), which are present in fetal mouse gonads. Therefore, the main goal of this Research Project is to test the hypothesis that in utero exposure to BPA causes gonadal defects in fetal and adult life via ERs. We design two specific aims to 1) investigate whether loss of ERa or B in fetal gonads render embryos insensitive to deleterious effects of BPA in reproductive funcstions and 2) study whether overexpression of ER increases the susceptibility of embryos to in utero exposure of BPA. The proposed experiments take advantage of the power of transgenic mouse models in combination of classic toxicological approaches. This project will not only provide animal models to test hypotheses that human models cannot, but also complementary information to interpret results of other components of the formative grant.